package com.lp.app.webserver;

import java.io.*;
import java.net.*;

//使用Socket創建一個WEB服務器，本程序是多線程系統以提高反應速度。
class WebServer
{
 public static String WEBROOT = "";//默認目錄
 public static String defaultPage = "index.htm";//默認文件
 public static void main (String [] args) throws IOException
 {
 System.out.println ("服務器啟動...\n"); 
 //使用8080端口提供服務
 ServerSocket server = new ServerSocket (8080);
 while (true)
 {
  //阻塞，直到有客戶連接
  Socket sk = server.accept ();
  System.out.println ("Accepting Connection...\n");
  //啟動服務線程
  new WebThread (sk).start ();
 }
 }
}


//使用線程，為多個客戶端服務
class WebThread extends Thread
{
 private Socket sk;
 WebThread (Socket sk)
 {
  this.sk = sk;
 }

 //線程體
 public void run ()
 {
  InputStream in = null;
  OutputStream out = null;
  try{
  in = sk.getInputStream();
  out = sk.getOutputStream();
  //接收來自客戶端的請求。
  Request rq = new Request(in);
  //解析客戶請求
  String sURL = rq.parse();
  System.out.println("sURL="+sURL);
  if(sURL.equals("/")) 
   sURL = WebServer.defaultPage;
  Response rp = new Response(out);
  rp.Send(sURL); 
  }
  catch (IOException e)
  {
  System.out.println (e.toString ());
  }
  finally
  {
  System.out.println ("關閉連接...\n");
  //最后釋放資源
  try{
   if (in != null)
   in.close ();
   if (out != null)
   out.close ();
   if (sk != null)
   sk.close ();
  }
  catch (IOException e)
  {
  }
  }
 }
}

package com.lp.app.webserver;

import java.io.*;
import java.net.*;

//獲取客戶的HTTP請求，分析客戶所需要的文件
public class Request{
 InputStream in = null;

 //獲得輸入流。這是客戶的請求數據。
 public Request(InputStream input){
 this.in = input;
 }

 //解析客戶的請求
 public String parse() {
 //從Socket讀取一組數據
 StringBuffer requestStr = new StringBuffer(2048);
 int i;
 byte[] buffer = new byte[2048];
 try {
 i = in.read(buffer);
 }
 catch (IOException e) {
 e.printStackTrace();
 i = -1;
 }
 for (int j=0; j<i; j++) {
 requestStr.append((char) buffer[j]);
 }
 System.out.print(requestStr.toString());
 return getUri(requestStr.toString());
 }

 //獲取URI信息字符
 private String getUri(String requestString) {
 int index1, index2;
 index1 = requestString.indexOf(' ');
 if (index1 != -1) {
 index2 = requestString.indexOf(' ', index1 + 1);
 if (index2 > index1)
  return requestString.substring(index1 + 1, index2);
 }
 return null;
 }
}

package com.lp.app.webserver;

import java.io.*;
import java.net.*;

//獲得用戶請求后將用戶需要的文件讀出，添加上HTTP應答頭。發送給客戶端。
public class Response{
 OutputStream out = null;

 //發送請求的文件
 public void Send(String ref) throws IOException {
 byte[] bytes = new byte[2048];
 FileInputStream fis = null;
 try {
 //構造文件
 File file = new File(WebServer.WEBROOT, ref);
 if (file.exists()) {
  //構造輸入文件流
  fis = new FileInputStream(file);
  int ch = fis.read(bytes, 0, 2048);
  //讀取文件
  String sBody = new String(bytes,0);
  //構造輸出信息
  String sendMessage = "HTTP/1.1 200 OK\r\n" +
  "Content-Type: text/html\r\n" +
  "Content-Length: "+ch+"\r\n" +
  "\r\n" +sBody;
  //輸出文件
  out.write(sendMessage.getBytes());
 }else {
  // 找不到文件
  String errorMessage = "HTTP/1.1 404 File Not Found\r\n" +
  "Content-Type: text/html\r\n" +
  "Content-Length: 23\r\n" +
  "\r\n" +
  "<h2>File Not Found</h2>";
  out.write(errorMessage.getBytes());
 }

 }
 catch (Exception e) {
 // 如不能實例化File對象，拋出異常。
 System.out.println(e.toString() );
 }
 finally {
 if (fis != null)
  fis.close();
 }
 }

 //獲取輸出流
 public Response(OutputStream output) {
 this.out = output;
}

}